1. Field of the Invention
The present invention relates to a scanner, and more particularly, to a scanner that has a movable mirror set inside its scanning module for increasing the resolution of scanned images.
2. Description of the Prior Art
FIG. 1 is a perspective view of a prior art scanner 10. The scanner 10 comprises a housing 12, a transparent platform 14 onto which a document 18 is placed, and a scanning module 16 for scanning the document 18. The operator of the scanner 10 lays the document 18 face down on the transparent platform 14. The scanning module 16 moves along a track inside the housing 12 and reads the document 18 through the transparent platform 14.
FIG. 2 is a cross-sectional view of the scanning module 16 cut along line 2xe2x80x942. The scanning module 16 comprises a light source 22, a fixed mirror set 23, a lens 26, and a charge coupled device (CCD) 28. As the scanning module 16 moves across the document 18, the light source 22 illuminates the document 18. The image of the illuminated document 18 is reflected by the mirror set 23. The lens 26 then focuses the image of the document 18 onto the CCD 28.
The resolution of the scanned image is determined by how many photosensitive cells are built into the CCD 28. Resolution is measured in dpi (dots per inch) and for a scanner 10 to scan at 600 dpi, 600 photosensitive cells must be built into each inch-long strip of the CCD 28. To increase the resolution to 1200 dpi, twice as many photosensitive cells must be used when manufacturing the CCD 28. As the desired resolution increases, the cost of manufacturing the CCD 28 increases. It is therefore an important objective to increase the resolution of the scanned image and still keep manufacturing costs low.
It is the primary objective of the claimed invention to provide a scanner in which a method may be employed to increase the resolution of a scanned image without increasing the number of photosensitive cells.
According to the claimed invention, the scanner comprises a housing, a transparent platform installed on the housing for placing a document, and a scanning module installed inside the housing for scanning the document. The scanning module comprises a first mirror set fixed inside the scanning module for reflecting light transmitted from the document, a second mirror set moveably installed inside the scanning module for changing an optical path of the light transmitted from the document so as to change resolution of a scanned image, and a lens set moveably installed inside the scanning module for focusing the light transmitted from the first and second mirror sets. When the second mirror set is moved to change the resolution of the scanned image, the lens set will move correspondingly to adjust the focus of the light transmitted from the first and second mirror sets.
It is an advantage of the claimed invention that the resolution of the scanned image can be increased without increasing the number of photosensitive cells built into the CCD.
These and other objects and the advantages of the present invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.